RNAi directs sequence-specific gene silencing by double-stranded RNA (dsRNA) which is processed into functional small inhibitory RNAs (˜21 nt). In nature, RNAi for regulation of gene expression occurs primarily via small RNAs known as microRNAs (miRNAs). Mature microRNAs (˜19-25 nucleotides) are processed from larger primary miRNA transcripts (pri-miRNAs) which contain stem-loop regions. Via a series of processing events catalyzed by the ribonucleases, Drosha and Dicer, the miRNA duplex region is liberated and a single strand (the antisense “guide” strand) is then incorporated into the RNA Induced Silencing Complex (RISC), thus generating a functional complex capable of base-pairing with and silencing target transcripts. The mode of target repression primarily depends upon the degree of complementarity; transcript cleavage typically requires a high-degree of base-pairing, whereas translational repression and mRNA destabilization occurs when small RNAs bind imperfectly to target transcripts (most often in the 3′ UTR). Indeed for the latter, short stretches of complementarity—as little as 6 bp—may be sufficient to cause gene silencing.